As a rubber composition for an automobile tire, a conjugated diene-based polymer such as polybutadiene or a butadiene-styrene copolymer, and a rubber composition containing a reinforcing agent are used.
In recent years, with increased concern about an environmental problem, requirements of fuel cost-saving properties on an automobile have been increasing, and a rubber composition used in a tire for an automobile has also been required to be excellent in fuel cost-saving properties.
For example, as a polymer enhancing fuel cost-saving properties, and a polymer composition good in fuel cost-saving properties, JP-A-63-186748 has proposed a polymer obtained by living anion-polymerizing butadiene and styrene using alkyllithium as a polymerization initiator and, then, modifying one end of the resulting polymer with a dialkyl amino group-containing alkoxysilane compound, and a polymer composition containing the polymer and a reinforcing agent. JP-A-1-217011 has proposed a conjugated diene-based polymer in which one end of a polymer obtained by copolymerizing butadiene and styrene using alkyllithium as a polymerization initiator is modified with bis(dimethylamino)methylvinylsilane, and a polymer composition of the polymer and reinforcing agent. JP-A-7-82422 has proposed a polymer obtained by living anion-polymerizing butadiene, styrene and (1-pyrrolidinyl)methylstyrene using alkyllithium as a polymerization initiator, and a polymer composition containing the polymer and a reinforcing agent.